The human body has numerous vessels carrying fluid to essential tissues and areas for recirculation or excretion. When vessels become damaged, severed or wholly occluded due to physiological problems, certain sections must be bypassed to allow for the free and continuous flow of fluids. Anastomosis is performed for the purpose of connecting different conduits together to optimize or redirect flow. In cardiac surgery, anastomosis is done to bypass the occluded vessel by harvesting a portion of an unobstructed vessel and joining it to the occluded vessel below the point of stenosis.
The common procedure for performing the anastomosis during bypass surgery requires the use of very small sutures, loupes and microsurgical techniques. Surgeons must delicately sew the vessels together being careful not to suture too tight and tear the delicate tissue, thereby destroying the vessel. Long term patency of anastomosis is also an issue. Exposure of damaged vessel wall to the bloodstream can lead to formation of thrombus and possible occlusion of the artery. As cardiac surgery is moving into less invasive procedures, surgical access is being reduced, forcing surgeons to work in a constantly tighter and tighter spaces. The procedures are made more difficult due to the multiple characteristics that are unique to each anastomosis. The arteries internal diameters dimensions are hard to predict, the walls can be friable and easy to tear, often, they are covered with layers of fat, others are deeply seated in the myocardium. Cardiac surgeons sometimes inadvertently suture too loosely, resulting in leakage of fluid from the anastomosis. Leakage of fluid from the area can cause serious drop in blood pressure, acute or chronic and general changes that may endanger life or induce local scar tissue to develop and often results in further blockage or damage to the sewn vessel.
Furthermore, anastomosing blood vessels may involve risks of physical injuries to the patient. For example, when performing coronary artery bypass grafting (CABG) procedures anastomosis often requires manipulation of the heart, so surgeons may access the back of the heart as well as the front. Patients supported by cardiopulmonary bypass during the procedure risk post-surgical complications that vary directly with the duration for which the heart is under cardioplegic arrest. In addition, surgeons performing anastomosis on a beating heart risk the possibility of a hemodynamic compromise during longer procedures. Consequently, surgeons are constantly searching for techniques to both reduce the risk of tissue damage as well as the laborious and time-consuming task of vessel suturing.
Stapling and coupling procedures have been used in performing large conduit anastomosis. While stapling is successful in gastrointestinal procedures due to the large size and durability of the vessels, it is less adequate for use in vascular anastomosis. The stapling instruments are difficult to reduce to the size required by smaller vessels like coronary arteries. When the staples are adapted to conform to the smaller sized vessels, they are difficult to maneuver and require a great deal of time, precision, and fine movement to successfully approximate the tissue. Often stapling or coupling devices require the everting of the vessel walls. Everting may not always be practical especially for small arteries because they may tear if everted. Furthermore due to issues related to tissue capturing at the edges, the force required to trigger the stapling devices and spacing between staple points, the potential of vessel laceration or leakage from the anastomosis exists just as it does in suturing. Stapling devices also are poor at conforming to different size vessels.
In view of the need for a better way connecting various sizes and consistency vessels and the difficulties encountered in doing so, there remains a significant need for implantable medical devices which can facilitate joining vessels of different characteristics.